For meeting requirements on orientation to service traffic which will dynamically change in the future and efficient utilization of bandwidth resources, an industrial community proposes a concept of an OBRing based on all-optical packet transmission and switching. The OBRing may greatly reduce a cost of software and hardware of an existing network and a cost of operation administration and maintenance of the existing network, and the OBRing is particularly suitable for a network full-interconnection application scenario of establishing a connection between any two points.
The OBRing may adopt a single-ring or double-ring topology. For example, as shown in FIG. 1, four nodes A, B, C and D are connected together through a single ring. An OBRing consists of a control plane and a data plane, which respectively use different working wavelengths. For the control plane, a master node A controls bandwidth resources of whole network in a centralized manner. A control frame sent by the master node A is transmitted by one circle around the single ring to distribute bandwidth grants to nodes B, C and D, and returns to the master node A with bandwidth requests of the nodes B, C and D. The master node A updates the bandwidth grants according to the bandwidth requests. For the data plane, at least one Optical Burst (OB) with a fixed length of each OB is used to bear one or more services in the OBRing. A duration of each OB is defined as an OB timeslot. OBs which are sent by different nodes and have different wavelengths are temporally aligned, that is, OBs with different wavelengths may share the same OB timeslot. The OBs are all-optically and transparently transmitted through nodes through which the OBs pass without optic-electro-optic conversion.
Each node broadcasts one or more OBs in at least one OB timeslot specified by the bandwidth grants by virtue of a fixed wavelength. The nodes update the bandwidth grants every one or more OB timeslots. An updating period of the bandwidth grants is defined as a Dynamic Bandwidth Assignment (DBA) period. After an OB arrives at a destination node, the destination node configures a tunable receiver according to a control frame, and receives the OB on a specified wavelength in a specified timeslot. The OB may be transmitted by an upstream node of the master node, and ends at a downstream node of the master node to establish an over-the-master-node connection or a not-over-the-master-node connection after being transparently transmitted over the master node, as shown in FIG. 2. A data connection may be established between any two nodes by sending and receiving one or more OBs, and a bandwidth of the data connection may be dynamically regulated by regulating the number of the one or more OBs. From the above, characteristics of the OBRing may be summarized as follows: a ring topology and multiple working wavelengths are adopted, the master node is adopted for centralized control, all-optical burst transmission and switching is supported, and a dynamic network full-interconnection application scenario is supported.
A method for bandwidth assignment is one of key technologies for implementing an OBRing. However, in the related art, above method for bandwidth assignment may not be directly applied to the OBRing.
As shown in FIG. 3, as an optical access network, a Passive Optical Network (PON) adopts a point-to-multipoint tree topology. An Optical Line Terminal (OLT) is connected with multiple Optical Network Units (ONUs) through an Optical Distribution Network (ODN). A direction from each ONU to the OLT is defined as an uplink direction. The OLT controls uplink bandwidth assignment of the PON in a centralized manner. The OLT periodically sends bandwidth grants to all the ONUs. The ONUs send uplink services to the OLT at different time with the same working wavelength according to the bandwidth grants, and report bandwidth requests. The OLT receives all the uplink services and bandwidth requests, and makes new bandwidth grants according to the bandwidth requests.
Such a method for bandwidth assignment for the PON is inapplicable to the OBRing. First, connections are established between one point and multiple points in the PON, while a connection is established between any two points in the OBRing, so that the method for bandwidth assignment for the PON only involves fair and effective bandwidth sharing of different sources when solving multi-source and single-sink problems, but cannot simultaneously take fair and effective sharing of bandwidth resources between different destination nodes in the OBRing into account. Second, centralized control is performed in a tree topology in the PON, while centralized control is performed in a ring topology in the OBRing. A control frame in the OBRing is sent by the master node, and ends at the master node after being transmitted by a circle around the ring, and an OB which bears a service may be continuously transmitted after being transmitted over the master node, so that when the master node in the OBRing starts making a new bandwidth grant after receiving a bandwidth request in a certain control frame, an over-the-master-node connection established according to the control frame has not yet finished transmission of the OB, and the OB is required to be transparently transmitted over the master node for continuous transmission, which may cause a receiving conflict; however, in the PON adopting the tree topology, all bandwidths of the network are available when the OLT makes bandwidth grants; and therefore, the receiving conflict caused by the over-the-master-node connection in the OBRing cannot be solved by the method for bandwidth assignment for the PON.
As a metropolitan area network technology, a Resilient Packet Ring (RPR) adopts an opposite double-ring topology, and both a control plane and a data plane are implemented in an electric domain. The RPR adopts distributed bandwidth resource management, and a connection is established between any two points. As shown in FIG. 4, taking an inner ring for example, after service data enters a node, header detection is performed to determine to send a downlink service or a service which passes by to a transition buffer area. A uplink service of the node is also sent to the transition buffer area. If the transition buffer area of the node is congested, congestion information may be transmitted to each node on the ring. Each node limits uplink services entering the transition buffer area according to a congestion control algorithm by virtue of a regulator. Therefore, bandwidth resources of the whole network are regulated at a source node to be managed.
Such a method for bandwidth resource management for the RPR is also inapplicable to the OBRing. First, an OB in the OBRing is transparently transmitted through one or more nodes through which the OB passes in an optical domain without electric domain processing, and is not cached in one or more intermediate nodes, so that it may not be implemented that a service is cached by virtue of a transition buffer area and bandwidth resources are fairly and effectively shared at a source node by virtue of the congestion control algorithm like in the RPR. Second, the RPR adopts distributed bandwidth resource management, and each node autonomously sends and receives services in the electric domain, so that the receiving conflict caused by an over-the-master-node connection under centralized control in the OBRing may not be solved with reference to the method for bandwidth resource management for the RPR.
As shown in FIG. 5, a switching matrix realizes a fast packet forwarding function in a router. An elongated data packet is divided into cells with fixed lengths after entering the router. The cells enter an input port of the switching matrix, and are transmitted to an output port through the switching matrix. Finally, the cells are recovered into the data packet, and the data packet is transmitted out of the router. In the switching matrix, a scheduling algorithm is adopted to fairly and effectively establish a connection between any input port and output port. If the input port of the switching matrix is considered as a sender of a node in the OBRing, the output port is considered as a receiver and a connection between the input port and output port in the switching matrix is considered as a data connection established between a source node and a destination node in the OBRing by sending and receiving OBs, a connection may be fairly and effectively established between any two points in the OBRing with reference to the scheduling algorithm of establishing a connection between any input port and output port in the switching matrix.
The scheduling algorithm for the switching matrix is not directly applicable to the OBRing. In the scheduling algorithm for the switching matrix, all the cells may pass through the switching matrix within one scheduling interval. During each scheduling, all connections between the input port and output port in the switching matrix are available. If the scheduling algorithm is directly applied to the OBRing, the receiving conflict caused by the over-the-master-node connection may occur. Therefore, the scheduling algorithm for the switching matrix may not be directly adopted for solving bandwidth assignment problems of the OBRing. Therefore, the bandwidth assignment problems of the OBRing may not be solved in the related art.